Arctic Tern
Posted: Sat Jun 22, 2013 1:08 pm
328. Arctic Tern Sterna paradisaea (Arktiese sterretjie)
Order: Charadriiformes. Family: Laridae
Description
Length 33–39 cm, weight 76-116 g. They are white with black caps and grey mantles, and a deeply-forked tail. In breeding season, the entire bill is blood-red. Their legs are so short that the birds appear to be crouched when standing.
Breeding adult: Black forehead, nape and crown and white cheeks; the mantle, back and upper wings are grey with the area near the wingtip being translucent and the collar, rump and underwing are white. The deeply forked tail is white with grey outer webs. The long bill, legs and feet are red.
Non-breeding adult and immature: Forehead white, crown streaked black and white, nape black. The bill is black and the legs and feet dark red to blackish. In flight, in non-breeding plumange the grey back contrasts with white rump and tail while all primaries appear translucent.
Juveniles differ from adults in their black bill and legs, "scaly" appearing wings, and mantle with dark feather tips, dark carpal wing bar, and short tail streamers.
Similar species: Compared to the Common Tern, it has a longer tail and mono-coloured bill. The non-breeding adult resembles the Antarctic Tern, but Antarctic Tern retains breeding plumage from October to April, and Arctic Tern from April to September.
Juvenile differs from juvenile Common Tern by its reduced carpal bar and pale secondaries, and by the marked contrast between the white rump and the grey back.
Distribution
Breeds from North America to the White Sea of Russia, heading south in the non-breeding season to the Southern Ocean and adjacent cold sea in the Humboldt Current passing South America and the Benguela Current passing southern Africa. Within southern Africa it is uncommon off the west coast, while more scarce further out to sea and off the southern and eastern coast of the region.
Habitat
Oceans. Pelagic, sometimes roosts ashore.
Movements and migrations
The Arctic Tern is well known for its long yearly migration. It travels from its Arctic breeding grounds to its wintering grounds off of Antarctica. It covers up to 40,000km which is the farthest yearly journey of any bird. It is mainly passage migrant through southern African waters, occurring from September-January.
Diet
It eats small fish or marine crustaceans.
Breeding
Breeding begins around the third or fourth year. They mate for life, and in most cases, return to the same colony each year. Courtship is elaborate and begins with a so-called "high flight", where a female will chase the male to a high altitude and then slowly descend. This display is followed by "fish flights", where the male will offer fish to the female. Courtship on the ground involves strutting with a raised tail and lowered wings. After this, both birds will usually fly and circle each other. The nest is usually a depression in the ground and 1-3 mottled eggs are laid. Both sexes share incubation duties. The young hatch after 22 to 27 days and fledge after 21 to 24 days. They nest once every one to three years (depending on its mating cycle); once it has finished nesting it takes to the sky for another long southern migration.
Call
Shrill short kik-kik in flight. Listen to Bird Call.
Status
Fairly uncommon but regular passage migrant and summer visitor. The Arctic Tern is classified as Least Concern (LC) on the IUCN Red List.
Order: Charadriiformes. Family: Laridae
Description
Length 33–39 cm, weight 76-116 g. They are white with black caps and grey mantles, and a deeply-forked tail. In breeding season, the entire bill is blood-red. Their legs are so short that the birds appear to be crouched when standing.
Breeding adult: Black forehead, nape and crown and white cheeks; the mantle, back and upper wings are grey with the area near the wingtip being translucent and the collar, rump and underwing are white. The deeply forked tail is white with grey outer webs. The long bill, legs and feet are red.
Non-breeding adult and immature: Forehead white, crown streaked black and white, nape black. The bill is black and the legs and feet dark red to blackish. In flight, in non-breeding plumange the grey back contrasts with white rump and tail while all primaries appear translucent.
Juveniles differ from adults in their black bill and legs, "scaly" appearing wings, and mantle with dark feather tips, dark carpal wing bar, and short tail streamers.
Similar species: Compared to the Common Tern, it has a longer tail and mono-coloured bill. The non-breeding adult resembles the Antarctic Tern, but Antarctic Tern retains breeding plumage from October to April, and Arctic Tern from April to September.
Juvenile differs from juvenile Common Tern by its reduced carpal bar and pale secondaries, and by the marked contrast between the white rump and the grey back.
Distribution
Breeds from North America to the White Sea of Russia, heading south in the non-breeding season to the Southern Ocean and adjacent cold sea in the Humboldt Current passing South America and the Benguela Current passing southern Africa. Within southern Africa it is uncommon off the west coast, while more scarce further out to sea and off the southern and eastern coast of the region.
Habitat
Oceans. Pelagic, sometimes roosts ashore.
Movements and migrations
The Arctic Tern is well known for its long yearly migration. It travels from its Arctic breeding grounds to its wintering grounds off of Antarctica. It covers up to 40,000km which is the farthest yearly journey of any bird. It is mainly passage migrant through southern African waters, occurring from September-January.
Diet
It eats small fish or marine crustaceans.
Breeding
Breeding begins around the third or fourth year. They mate for life, and in most cases, return to the same colony each year. Courtship is elaborate and begins with a so-called "high flight", where a female will chase the male to a high altitude and then slowly descend. This display is followed by "fish flights", where the male will offer fish to the female. Courtship on the ground involves strutting with a raised tail and lowered wings. After this, both birds will usually fly and circle each other. The nest is usually a depression in the ground and 1-3 mottled eggs are laid. Both sexes share incubation duties. The young hatch after 22 to 27 days and fledge after 21 to 24 days. They nest once every one to three years (depending on its mating cycle); once it has finished nesting it takes to the sky for another long southern migration.
Call
Shrill short kik-kik in flight. Listen to Bird Call.
Status
Fairly uncommon but regular passage migrant and summer visitor. The Arctic Tern is classified as Least Concern (LC) on the IUCN Red List.